Hearing Loss Is Possibly Reversible

About 16,000 inner ear hair cells are involved in hearing and balance. This number goes down as people get older because these cells don't spontaneously regenerate. Hearing loss, without the assistance of a hearing aid or implantable device, is usually irreversible.

Scientists at the University of Virginia Health System, Massachusetts General Hospital and Harvard Medical School found that blocking a gene called retinoblastoma, expressed in the nuclei of inner ear hair cells, seemed to produce more than the normal amount of hair cells in developing mice. These cells were also found to be entering the ‘cellular cycle,' replicating DNA.

"This discovery may be important for our efforts to develop the capacity to treat irreversible hearing and balance loss,” said Jeffrey Corwin, Ph.D., professor of neuroscience at the University of Virginia. "It may one day be possible to devise drug treatments that selectively disable the retinoblastoma protein on an as-needed basis to allow hair cells to regenerate.”

Corwin cautioned that the retinoblastoma protein also helps to stave off cancer as a known tumour suppressor gene and should not be turned off indefinitely.

Corwin explained that inner ear hair cells, like nerve cells, lose their ability to replicate as they become specialized in the body during embryonic development. But this study showed that hair cells can continue to divide, in the absence of the retinoblastoma protein, so that functional hair cells can be generated through the cell division of preexisting hair cells.

"Demonstrating that retinoblastoma critically regulates hair cell division opens new opportunities, both for hair cells regeneration and for creating cells lines for hearing research,” Corwin and his colleagues wrote.